The European Stinging Nettle is actually native to several places around the world, including the western United States. However, it has been introduced to the eastern United States, including the Appalachian Trail.

This invasive plant has actually been in use since at least the 10th Century with the Anglo-Saxon pagans. They used it as a remedial herb and its use in traditional medicine has remained popular ever since. It is unknown when it was introduced to North America, but it was likely shipped from Europe for medicinal cultivation.

Even though it has a positive impact in this light, those who may live near the Appalachian Trail need to keep any of these plants on their property under control. This is because once the European Stinging Nettle becomes established, it can grow in thick patches.

Be leery of this plant. Many fine bristles grow on its stems, and contact with them causes burning sensations and blistering. On the Appalachian Trail, it is prolific, so it can block access to areas with its thick growth and stingers.

This plant is not only dangerous because of its stingers: its dense growth also poses a threat to the Appalachian Trail ecosystems on land. This is because it grows quickly, so it has a tendency to outperform surrounding plants in the attainment of sunlight and nutrients. Thus, it threatens the diversity of the Trail's ecosystems. 

Chinese silvergrass was originally brought to the U.S. as a decorative plant during the late 1800's. It was often planted along roadways for the aiding of scenery, which is interesting because automobiles began to appear during the same time period, thus necessitating more roads.

This is an aggressive plant in its spread. Considering the fact that it thrives in temperate regions, the Appalachian Trail is a very suitable habitat for it. Its aggression lies in its spread; the plant can even spread from pots into other areas, likely because its seeds can be blown by the wind.

Another important thing to consider when looking at this plant in the context of the Appalachian Trail is the fact that it presents a major fire hazard. This is because it is often dry, and thus flammable as a result. This is especially threatening because the Appalachian Trail goes through many forests along its length, thus furthering the dangers of fire.

As is typical with other invasive plants, Chinese silvergrass is also damaging to the trail's ecosystem because it has a tendency to displace native plants, mostly because of its dense growth forms, easy spread, and tall growth. True to its 19th Century introduction, Chinese silvergrass is still a common sight along the trail's roads.